European Space Agency

AlphaSat TDP#4: T6 Ion Thruster


The T6 High Power Electric Propulsion System (HPEPS) was selected in September 2004 as most promising candidate for a future a high-power Electric Propulsion solution for the AlphaBus Extended range. Full development and qualification is now funded within the scope of the AlphaBus Parallel Development line up to and including a full end-to-end qualification of the T6 Thruster, Power Supply (PSCU) and Mechanism (EPPM).

The use of Gridded-Ion thrusters on Telecommunications spacecraft is perceived to be risky following a number of failures on similar technology U.S. Ion Propulsion systems. To mitigate the risk of adopting new technology the T6 HPEPS will be individually qualified and then a fully representative system life test including a qualification margin of 50% shall be completed. However, no ground test may fully represent the spacecraft environment, and ground testing can thus only approximate, sometimes separately, the combined effects that will be seen from sun angle and radiation, thermal and mechanical constraints including launch, true vacuum, plume impingement and spacecraft charging to mention a few examples.

Consequently the objective of the T6 TDP is to validate in-flight T6 ion thrusters and associated system. Thereby space flight heritage will be acquired providing full confidence in the T6 HPEPS and allaying the concerns of a typical customer. The T6 under test in the QinetiQ electric propulsion facilities at Farnborough is shown in the photograph below.

  click for larger image


The T6 TDP has to be defined as such that it does not impact the AlphaSat platform and payload operations. The T6 TDP accommodation, power requirements and operational constraints are the key issues at present.


The T6 Ion thruster is the world's most advanced ion thruster with significant advantages of weight, lifetime, and specific impulse over its nearest competitors. The EPPM mechanism represents a new, versatile and lightweight concept for pointing mechanism's with significant potential advantages compared to the current European generation of thrusters. The PSCU power supply incorporates a number of truly innovative features which have given it significant mass advantages over other comparable designs.


The T6 TDP system architecture is currently being defined. It is proposed to be essentially half a T6 HPEPS and will include:

  • QinetiQ Ltd's T6 Ion Thruster,

  • Marotta UK's Xenon Flow Control Unit (XFCU),

  • EADS Astrium CRISA's Power Supply and Control Unit (PSCU), and

  • Austrian Aerospace's Electric Propulsion Pointing Mechanism (EPPM).

The T6 HPEPS system architecture is shown in the figure below.

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The Phase A study is to confirm the feasibility of the T6 TDP for AlphaSat by the end of July 2006.

Current status

Phase A commenced on 6 February 2006 and was completed on 29 September 2006. Following the successful Phase A study on the T6 TDP for Alphasat the next steps will be to complete the development phases B0, B, C and D leading to the integration of the T6 TDP with the Alphasat spacecraft.
The operation of the T6 TDP for a period of 3 years is planned to achieve the in-flight heritage for the T6 HPEPS.

Status date

Wednesday, November 26, 2008 - 11:56